..."Asteroid belts similar to the one between Mars and Jupiter appear to be rare beyond our solar system, implying that complex alien life may be rare as well, a new study reports. Fewer than 4 percent of known alien solar systems are likely to have an asteroid belt like the one in our own neck of the woods, researchers found. Belts that look like ours may help spur the evolution of life, seeding rocky planets with water and complex chemicals but not pummeling the worlds with a constant barrage of violent impacts."...